1. Field of the Invention
This invention relates to a camera and camera accessory mounting mechanism which enables accessory devices to be mounted to and dismounted from a camera.
2. Prior Art
A typical conventional accessory shoe on the camera side and accessory foot on the accessory side used to mount accessory devices such as electronic flash devices to a camera are shown in the plane and cross section drawings of FIG. 24 (a) and (b), respectively. With this device, the electronic flash is mounted to the camera by inserting a foot 72, which is a mounting member on the electronic flash, in an accessory shoe 71, a mounting member of the camera. When the foot 72 is thus mounted in the accessory shoe 71, positioning on the right and left sides as seen in the figure (hereinafter referred to as horizontal (lateral) positioning) is accomplished by parallel sides 61 of the foot 72 and parallel inside faces 62 of the accessory shoe 71, and positioning in the up and down directions as seen in the figure (hereinafter referred to as vertical positioning) is accomplished by turning a nut 73 to press upper inside faces 63 of the accessory shoe 71 against faces 64 of the foot 72 together. At this time, front ends of the sides 61 and faces 64 of the foot 72 used for horizontal (lateral) and vertical positionings, respectively, are at the same position.
In recent cameras, single lens reflex cameras equipped with an autofocus mechanism (AF) have become predominant in the SLR market, and accessory electronic flash devices provided with an auxiliary light source function to enable accurate automatic focusing in dark situations have become common. However, the mounting devices used with these electronic flash devices are subject to gradual loosening and play, resulting in misalignment of the optical axes of the light beam emitted from the auxiliary light source and a taking lens of the camera, and thus limiting the effective range of the auxiliary light to the extreme. It therefore becomes necessary to increase the precision of mounting the electronic flash to the camera.
However, in the case of the conventional camera and accessory device mounting mechanism such as shown in FIGS. 24 (a) and (b), because horizontal (lateral) positioning is determined by the widest part of a fit surface of the foot 72, specifically by the sides 61 of the foot 72 and the inside faces 62 of the accessory shoe 71, when the accessory foot 72 is inserted into the accessory shoe 71, a large turning moment centering on contact portions of the sides 61 of the foot 72 and the inside faces 62 of the accessory shoe 71 occurs, and it is therefore possible for the foot 72 to be mounted on a bias causing the mounting of the accessory difficult. This can be prevented by providing sufficient space between the foot sides 61 and shoe's inside faces 62, but this would in turn increase the play in the lateral direction. Conversely, if the gap between the foot sides 61 and shoe's inside faces 62 is narrowed to control play in the horizontal (lateral) direction, the foot 72 will catch in the accessory shoe 71 and it will not be easy to mount and dismount the accessory device.
As also previously described, because the sides 61 of the foot 72 and the inside faces 62 of the accessory shoe 71 are parallel, the horizontal (lateral) positioning members of the accessory and camera mounting mechanisms overlap and fit together across the entire length of the sides 61 and the inside faces 62. Thus, the length of the fit surfaces of the accessory foot and accessory shoe when the accessory is mounted to the camera is long, and if the gap between the foot sides 61 and accessory inside faces 62 is narrowed to control play in the lateral direction, the foot 72 will bind or stick when the foot 72 is inserted to the accessory shoe 71 and easy mounting and dismounting will not be possible. In addition, even if the foot 72 does not bind, the friction generated during mounting and dismounting will be great and mounting and dismounting will be difficult.
Furthermore, because the width of the foot 72 at the front end in the direction of insertion (the distance between the sides 61) and the width of the insertion opening at the back of the accessory shoe 71 (the distance between the inside faces 62 of accessory shoe 71) are approximately equal, it is difficult to properly position the foot 72 to the insertion opening of the accessory shoe 71 when mounting the accessory.
Moreover, because the front ends of the sides 61 used for horizontal (lateral) positioning is at approximately the same position as the front of the faces 64 used for vertical positioning in the mounting mechanism of the flash device as described above, when the flash foot 72 is inserted to the accessory shoe 71, mating positions in both the horizontal (lateral) and vertical directions must be located at the same time, and it can therefore be difficult to mount the foot 72 to the accessory shoe 71 quickly.
Furthermore, some recent cameras have an accessory shoe like the one as shown in FIG. 24(a) which is provided with signal terminals 65, 66, 67 inside for sending and receiving signals between the electronic flash and camera so as to control the electronic flash.
However, because the conventional camera and accessory device mounting mechanism as described above regulates horizontal (lateral) positioning with the sides 61 of the foot 72 (i.e., the widest part of foot 72) and the inside faces 62 of the accessory shoe 71, and provides the signal terminals 65, 66, 67 between those inside faces 62, these signal terminals 65, 66, 67 are exposed on the top at a position where they can be touched relatively easily, and they are often touched accidentally by the operator. As a result, the surface of the signal terminals 65, 66, 67 corrode and poor contact easily occurs.
Furthermore, in cameras of the type which control the electronic flash with a control signal sent from the control circuitry in the camera, because the signal contacts connected directly to the control circuitry are similarly located in the wide area between the inside faces 62 of accessory shoe 71 where they are thus exposed to the outside, the electrical circuit elements of the camera may be adversely affected by static electricity.
Furthermore, in cameras which supply electrical power to the electronic flash and in the electronic flash devices which draw their power supply from such a camera, power supply contacts are also included in the signal contacts described above. In this case, too, it is similarly difficult to locate the power supply contacts in the accessory shoe in a position where they are not easily touched, and it is possible to accidentally touch both the accessory shoe and power supply contacts simultaneously and thus establish conductivity.